1. Field of the Invention
The present invention relates to a device for refrigeration by evaporation and adsorption, whose principle consists in evaporating a liquid under the effect of a depression sustained by adsorption of the vapors of said liquid. It is the evaporation of this refrigerant liquid contained in an evaporator (a chamber, cavity or the like) that prompts a cooling in the vicinity of the evaporator. Another chamber, containing adsorbent material, is generally connected to the evaporator.
2. Description of the Prior Art
The principle of refrigeration by evaporation of a refrigerant liquid and adsorption of vapor of this liquid has undergone numerous developments, both for cyclical systems (with regeneration of adsorbents by heating) and for single-use systems.
In all these devices, the adsorption is accompanied by heat dissipation in the adsorbent leading to a rise in temperature which it is sought to limit by discharging a part of this heat.
The cyclical devices generally comprise adsorbents in connexion with heat exchangers which firstly discharge the heat dissipated by the adsorbents during the adsorption reaction of the refrigerant liquid vapors and secondly heat these adsorbents to regenerate them.
The principle of cyclical adsorption for refrigeration is described in the U.S. Pat. No. 4,637,218.
In the cyclical systems, a refrigerant liquid is evaporated by adsorption and then condensed, the adsorbents being regenerated by heating after having fulfilled their adsorption function. Heat exchangers are designed firstly to cool the adsorbents during their function of adsorption and secondly to heat these adsorbents for their regeneration.
One of the main difficulties of the cyclical devices lies in the efficiency of the heat coupling between the heat exchangers and the adsorbents. For example, efficient thermal coupling is difficult to achieve with zeolites which are very efficient adsorbents otherwise. Indeed, the adsorbents usually take the form of grains or rods having very poor heat conductivity. The result thereof is low efficiency of cyclical systems.
The U.S. Pat. No. 5,535,817 has efficiently analyzed these difficulties and proposes a method for forming zeolites by deposition on a metal surface giving greatly enhanced performance. The zeolites are directly deposited on the interior surface of metal tubes so as to form an internal lining. The method of deposition proposed in this patent is however complicated to implement. This makes it difficult to apply in the case of low-cost, large-scale production.
In the case of single-use devices, the U.S. Pat. No. 4,759,191 proposes to limit the rise in temperature by the addition to the adsorbents of different materials, especially materials having a solid-liquid phase change between 30° C. and 70° C. To obtain a significant effect, it is necessary however to have a large quantity of solid-liquid phase-changing materials (typically twice as much as the adsorbents to get a significant effect). This U.S. Pat. No. 4,759,191 also mentions the possibility of using a liquid-gas phase-changing material as well as adsorbent temperatures of up to 100° C. or even 110° C. However, the constraints related to the implementation of such a device are not analyzed.